A high-voltage electric power circuit for controlling an electric machine such as a multi-phase electric motor/generator may include a high-voltage DC power source that is electrically connected to a front-end DC-to-DC electric power converter (hereafter ‘front-end converter’) to increase voltage level that is supplied to a high-voltage DC bus of an inverter. A bulk capacitor may be arranged across the high-voltage DC bus to provide electrical stability and store supplemental electric energy. Operation and control of electric machines, such as permanent magnet synchronous electric motors may be accomplished by employing the inverter to transform DC electric power to AC power using pulsewidth-modulated (PWM) control signals that are output from a controller. Known inverters may be controlled in different operation modes, including PWM modes such as sine, hysteresis, over-modulation or space vector PWM modes, a six-step mode, or another suitable mode.
Occurrence of an open circuit fault or a short circuit fault in a high-voltage electric power circuit may result in operating the electric machine in an uncontrolled generator (UCG) mode.